Electrostatic heating



May 16, 1950 J. E. DUFF 2,507,964

ELECTROSTATIC HEATING Filed Nov. 24, 1944 I 2 Sheets-Sheet 2 sole plate rises to a predetermined temperature the bimetallic strip 31 ilexes upwardly to the position shown in Figure 1, to interrupt the flux path between the sole plate sections 29 and 30.

The temperature at which the bimetallic strip 31 operates is selectively controlled by means of a rod 42 threaded into a nut 43 molded into a platform 44 extending between the front and rear legs of the handle 21. The rod 42 is adjusted by an indicator knob 45 to alter the spacing of the lower end 46 of the rod 42 with respect to the bimetallic strip 31 to thereby vary the temperatures at which the flux path between the sole plates 29 and 38 will be interrupted. An unshown dial is mounted on the upper surface of the platform 44 and cooperates with the pointer 41 on the knob :i5 to indicate the temperature setting of the thermostat 36 at which the latter will operate to interrupt the flux path between the sole plate sections 29 and 3U. Ir desired, the 'dial' may be calibrated for different materials to be ironed to indicate the setting for the parlticular type of material at which the thermostat will operate to provide the required temperature for ironing.

When the iron 25 is placed upon the base I2, the sole plate sections 29 and 30 in the majority of positions form the third plate in the capacitor system and provide a return path for the electrostatic flux between the adjacent electrodes I and I6, while the material 48 being ironed between the sole plate and electrodes acts as a dielectric in the capacitor system and is thereby heated for the ironing operation.

In the ironing operation, the generator 2| is set to provide a frequency which is best suited for the material 48 to be ironed and the thermostat knob 45 is adjusted to the desired temperature. Placing the iron on the material 48 capacitatively couples the sole plate sections 29 and to the underlying electrode strips I5 and IS of opposite polarity, while the material 48 acts as a dielectric therebetween to thereby generate heat in that part of the material 48 which is' beneath the iron as the latter is moved over the electrodes. Thus the dielectric loss in the material 58 being ircned is converted into electrostatic heat for ironing the material.

In Figure 3 is disclosed a variety of positions which the iron 25 might take with respect to the electrode strips I5 and I6 during the ironing operation. Positions A', B', C and D in Figure 3 correspond to the positions A, B, C and D .of Figures 4 and 5, and show the different flux paths which are dependent upon the position oi the iron 25 relative to the electrodes. When the iron 25 is in position A and the thermostat 36 open, each of the sole plate sections 29 and 39 completely cover an electrode of opposite polar- A'ity as shown at A in Figure 4, but since the sole plate sections 29 and 39 do not span adjacent electrodes of opposite polarity, no flux path is provided therebetween, with the result that no heating occurs in the material 48 being ironed. If the thermostat 36 is closed as shown in C of Figure 3 and at C in Figure 5, the thermostat 36 electrically connects the sole plate sections 29 and 38 to form in effect a unitary sole plate and provides a flux path for the electrostatic iield from the electrode I5 through the material 48 into the sole plate section 29, through the bimetallic strip 31 to the sole plate section 39 and thence through the material 48 to the electrode i6. In this position of the iron with the thermostat closed, the maximum possible iiux 4 flows to produce maximum heating in the dielectric material 48 since the total areas of the sole plate sections 29 and 3U are capacitatively coupled over electrodes I5 and I6 of opposite polarity.

If the iron is in the position shown at B' of Figure 3, and at B of Figure 4, each sole plate section 29 and 30 spans adjacent electrodes of opposite polarity and form their own ilux path through the material 48, although the thermostat 36 is open, to thereby heat the material 48. Thus each half of the sole plate sections 29 and 38 acts as a return path for the electrostatic flux from each electrode of opposite polarity, and since the areas of the sole plate sections 29 and 30 which are capacitatively coupled with electrodes of opposite polarity are not greatly unbalanced, the heat produced in the material 48 will be relatively close to the maximum. Ii the thermostat 36 is closed, as indicated at D in Figure 3 and D in Figure 5, the same quantity of flux ilow will be maintained because each half of the sole plate sections 29 and 30 continue to act as a return path for one-half of the electrostatic flux path from each electrode of opposite polarity to thereby continue to heat the material 48.

If the iron is in the position E shown in Figure 3, each half of the lateral widths of the sole plate sections 29 and 30 span electrodes of opposite polarity and provide a flux path to produce maximum heating in the dielectric material 48 being ironed.

When the iron is in the F position, the heating will be at a minimum since the the portions 52 of the sole plate sections 29 and 30 are capacitatively coupled to electrodes I5 of like polarity, and the area of such portions 52 are greatly unbalanced with respect to the area of the portions 53 which are coupled to the electrode I6 of opposite polarity.

In ironing position G, with the thermostat 36 open, each sole plate section 29 and 30 has a relatively small area 54 capacitatively coupled to electrodes of opposite polarity in comparison to the areas of the portions 55, so that each sole plate section is unbalanced over adjacent electrodes of opposite polarity with the result that less heat will be generated in the material 48. If the thermostat 36 is closed, as shown in ironing position H, greater heat will be generated in the material 48 since the thermostat electrically connects the sole plate sections 29 and 30 and the total area of the portions 54 and 55 capacitatively coupled to each electrode is more evenly divided over electrodes of opposite polarity.

Thus the movement of the iron over the material 48 causes a rapid change of flux paths in the sole plate sections 29 and 30, and the intensity of the heat supplied to the material 48 being ironed is varied by such movement of the iron and is dependent upon the relative areas of the sole plate sections which are capacitatively coupled with electrodes of opposite polarity. The thermostat 36 provides means for selectively controlling the ironing temperature by disconnecting the sole plate sections 29 and 30 to thereby interrupt the ux path therebetween and thus reduce the total area of the sole plate which is available to form the return ilux path so that the heat applied to the material 48 is reduced.

I claim:

1. An iron for use on an ironing surface having a high frequency eld, said iron comprising a body, a sole plate on said body formed in a plurality of spaced separate sections each to carry the flux of the high frequency field during the ironing of material on said surface, and a thermostat for electrically connecting said spaced sole plate sections upon a decrease in temperature below a given value and disconnecting them upon a rise in temperature above a given value whereby the high frequency flux produced by the eld will flow between said spaced sole plate sections with low sole plate temperatures and the flow of iiux therebetween will be interrupted with high sole plate temperatures and confined to flow in each spaced sole plate section.

2. An iron comprising an electrical insulating body, a sole plate on said body and formed in a plurality of separate sections, means electrically insulating said sections from each other, and a thermostat for electrically connecting said separate sections of said sole plate upon a decrease in temperature below a given value and disconnecting them upon a rise in temperature above a given value.

3. An iron for use on an ironing surface having a plurality of spaced high frequency electrodes, said iron including a sole plate formed of spaced metallic sections and forming the ironing surface of said iron, and thermostatic means for electrically connecting said spaced metallic sole plate sections upon a decrease in temperature below a given value and disconnecting them upon a rise in temperature above a given value whereby high frequency ux produced by the electrodes will flow between said sole plate sections with low sole plate temperatures and the ilow of flux will be interrupted with high sole plate temperatures.

4. Ironing apparatus comprising a support for the material to be ironed, a plurality of spaced electrodes in said support for connection to an oscillator, an iron having a sole plate of spaced metallic sections forming the ironing surface of said iron, each of said spaced sole plate sections forming a free electrode capacitively coupled to said electrodes to provide a flux path between adjacent electrodes when said sole plate sections are brought into ironing contact with the material on said support, and thermostatic means for electrically connecting said spaced metallic sole plate sections upon a decrease in temperature below a given value and disconnectlng them upon a rise in temperature above a given value whereby high frequency iiux produced by the electrodes will flow between said sole plate sections with low sole plate temperatures and the flow of flux will be interrupted with high sole plate temperatures.

5. An iron for use on an ironing surface having a plurality of spaced high frequency electrodes, said iron including a sole plate formed of spaced sections and forming the ironing surface of said iron, means electrically insulating said spaced sections from each other, each of said spaced insulated sole plate sections being capacitively connected to the electrodes to carry the high frequency ux produced by the electrodes during ironing of material on said surface, and thermostatic means for electrically connecting said spaced sole plate sections upon a decrease in temperature below a given value and disconnecting them upon a rise in temperature above a given value whereby high frequency flux produced by the electrodes will flow between said spaced sole plate sections with low sole plate temperatures and the flux will be interrupted with high sole plate temperatures and confined to flow in each spaced sole plate section.

JACK E. DUFF.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 757,139 McLaughlin Apr. 12, 1904 2,133,494 Waters Oct. 18, 1938 2,226,871 Nicholas Dec. 31, 1940 2,233,615 Kuhn et al. Mar. 4, 1941 2,298,037 Crandell Oct. 6, 1942 2,298,038 Crandell Oct. 6, 1942 2,345,413 Morton Mar. 28, 1944 2,402,575 Purpura June 25, 1946 2,449,317 Pitman Sept. 14, 1948 2,449,318 Pitman et al. Sept. 14, 1948 FOREIGN PATENTS Number Country Date 557,138 Great Britain Acc Nov. 5, 1943 118,453 Australia May 1l, 1944 OTHER REFERENCES Taylors A Radio-Frequency Gun, Electronics Nov. 1943 pag-es 106-111 and 310. 

